Application Scenarios
A mid-stream gas compressor station was living with a familiar problem: the discharge-pressure transmitter on the knock-out pot drifted just enough between cal cycles to make the anti-surge margin look softer than it was. The old unit was a passive 4–20 mA device — when the reading looked wrong, the control room had no way to tell whether the sensor was drifting, the impulse line was silting up, or the orifice was fouled. So they swapped guesswork for a 2051CG3A02A1AH2B2M5D4.
The 316L diaphragm and silicone fill handled the wet-gas condensate; the Coplanar flange went straight onto the existing 2-inch manifold with no new impulse piping. Within a week the HART diagnostics had flagged a slowly rising damping-time signature on one leg — a partially blocked impulse line, caught before it ever moved the setpoint. The tech trimmed zero from the local LCD during rounds, then confirmed the loop integrity from the DCS tag without a second trip to the skid.
The real story is not the accuracy number. It is that a single smart transmitter turned a “call the instrument crew” mystery into a diagnosed, scheduled repair — and the compressor never saw a spurious surge trip.
Parameter
| Parameter | Value / Description |
|---|---|
| Product Model | 2051CG3A02A1AH2B2M5D4 (Rosemount 2051C ordering-code string; stock also appears as 2051CG3A02A1AH2B2M5D4) |
| Manufacturer | Rosemount, Emerson Automation Solutions |
| Product Category | Coplanar Gage Pressure Transmitter with integrated HART communication electronics |
| Code Decoded — CG | CG = Coplanar, gage pressure. Process pressure referenced to ambient, not differential across two ports |
| Code Decoded — 3 | Range code 3: URL –393 to +1000 inH₂O (–0.98 to +2.5 bar), calibrated 0–1000 inH₂O in standard trim. Gage scale effectively 0–1000 inH₂O (≈0–2.5 bar / 0–36 psi) in the normal gage table; always confirm the nameplate cal range before re-ranging |
| Code Decoded — A | Output A = 4–20 mA with digital signal based on HART protocol. HART Revision 5 is the factory default; field- or factory-selectable to Revision 7 when option HR7 is specified |
| Code Decoded — 02 | Coplanar flange, flange and drain/vent material stainless steel. Direct 2-inch manifold mount, four-bolt pattern |
| Code Decoded — A1 | Isolating diaphragm 316L stainless steel with silicone oil fill fluid. The workhorse wetted-material pairing for water, steam-condensate, hydrocarbon and general process service |
| Code Decoded — AH | Housing: aluminum, polyurethane-coated, with ½-14 NPT conduit entry. Field-wiring and terminal access through the standard Rosemount housing cover |
| Code Decoded — B2 | Mounting bracket, carbon-steel type, panel-mount style in the 2051 table (the B-family bracket codes cover pipe- and panel-mount variants — verify the bent-plate orientation on the nameplate before ordering a replacement bracket) |
| Code Decoded — M5 | PlantWeb LCD indicator, 0–100% scale, driven by the local interface — read PV, units and status at the instrument without a communicator |
| Code Decoded — D4 | External configuration/zero-span button feature on the electronics, factory-specified option. Combine with M5 and you can do basic ranging and trim work at the device; exact hazardous-area certification should be read from the tag, not inferred from D4 alone |
| Output Signal | 4–20 mA DC, two-wire, loop-powered; HART FSK digital superimposed on the loop (Bell 202, 1200/2200 Hz) |
| Reference Accuracy | ±0.05% of calibrated span (typical, 2051C published grade). Total performance including linearity, hysteresis and repeatability; verify against the shipped Configuration Data Sheet |
| Turndown / Rangedown | Up to 100:1 on the 2051C platform. The same URL can be trimmed to a small operating band without changing the instrument |
| Long-Term Stability | ±0.125% URL over 5 years typical for the 2051C family — the number that actually drives calibration-interval extension |
| Supply / Loop Load | 10.5–55V DC loop supply (higher figure is the family upper limit; confirm against the approval sticker for IS restrictions). Load limits follow the usual HART curve: min. 250 Ω to pass digital comms, up to ≈650 Ω at 12V rising with supply voltage |
| Wetted Materials | 316L SST isolating diaphragm; silicone fill; O-ring is the code-2 family default — process-fluid compatibility must be checked against the fluid table (chlorine, strong oxidisers and high-temperature steam have their own rules) |
| Process Connection | Coplanar flange, 316L SST, drain/vent plug SST. No impulse piping or separate mounting bracket required |
| Environmental | –40 °C to +85 °C ambient operating; process temperature limits depend on diaphragm/fill/O-ring choice (silicone fill: consult the compensation table, roughly –40 °C to +120 °C process with appropriate flange rating) |
| Ingress / Enclosure | NEMA 4X / IP66–IP67 type sealed housing when the cover O-ring and conduit seal are correctly seated — the rating lives or dies by the installation, not the casting |
| Certifications | The D4/M5/AH combination commonly ships with FM hazardous-area approvals; the exact class, division, group and temperature code are printed on the approval label. Do not assume ATEX, IECEx or CSA from the ordering code — read the tag |
| Diagnostics | HART device variables, loop status, PV readback, damping, sensor-health and plugged-impulse-line / process-alert indicators when the transmitter is running the Advanced Diagnostics suite; accessible via 475/375 Field Communicator or AMS Device Manager |
